NEW YORK -- As Mayor Michael Bloomberg plans to take more than 6,000 teachers off the payroll to help balance a strained budget, some parent advocates are questioning what the layoffs will do to New York public school class sizes.

The proposed cuts, combined with attrition over the last two years, would take roughly one in eight teachers out of the city's public schools and could swell classes to an average of 24 to 29 kids, depending on grade level _far outstripping the national public school average. New York City education officials say they don't yet know exactly how the layoffs would impact class sizes.

City officials blame the drop on the loss of billions of dollars in state and federal aid. Parent advocates say the city is ignoring an already-broken agreement made in 2007 that was supposed to reduce class sizes across the board.